Pass CA certificates in parameters, not as path to file or folder

This PR implements feature that allows passing list of root and intermediate CA certificates as a list of strings - instead of path to file or path to folder. This is useful when there is no access to FS or do not want to access to FS and creates certificate pinning - sort of.

This feature has no unit tests (though all existing unit test pass) - please help me understand the structure of unit tests in the project so I can add some.